Hydrogen gas is a very desirable fuel because it can be reacted with oxygen in hydrogen-consuming devices, such as a fuel cell, combustion engine or gas turbine, to produce energy and water. The use of hydrogen gas can ameliorate environmental pollution; lessen the world's dependency on fossil fuels or petroleum; ease fears of depleted energy sources.
Safe and efficient storage of hydrogen is a prerequisite for widespread commercial use as a fuel. U.S. Pat. No. 6,534,033 B1 to Amendola et al., discloses the use of stabilized metal hydride solutions as an example of a safe, hydrogen-rich storage medium. Thus, with an abundant supply of metal hydride solutions, research is focused on the release of hydrogen from the storage medium.
The class of metal hydrides known as borohydrides is known to decompose in water, in the following manner: borohydride plus water yields metaborate and hydrogen gas. The chemical reaction illustrated with borohydride is:BH4−+2H2O═BO2−+4H2.
Hydrogen-rich borohydrides are also of interest in electroconversion cells where the alkali metal-containing compound, such as borohydride is oxidized to generate electricity (U.S. Pat. No. 5,804,329 to Amendola; U.S. Pat. No. 6,468,694 B1 to Amendola; and U.S. Pat. No. 6,554,877 B2 to Finkelshtain et al.). Although oxidation reactions are required to generate electric current, the spontaneous release of hydrogen gas when borohydrides are in contact with water is reported in each of the patents cited above. The borohydride decomposition reaction in water occurs very slowly without a catalyst. Thus, catalysts become the critical component in any hydrogen gas delivery system based on borohydride decomposition.
Catalysts used in hydrogen gas evolution or production of hydrogen compounds have been identified as amines (U.S. Pat. No. 3,923,966 to Vaughan); metal derivative catalysts (U.S. Pat. No. 4,448,951 to Rupert et al. and U.S. Pat. No. 6,387,843 B1 to Yagi et al.); and transition metal catalysts (U.S. Pat. No. 5,804,329 to Amendola and U.S. Pat. No. 6,534,033 B1 to Amendola et al.).
There is a need for a broader range of catalytic materials, so that there are more choices for use in hydrogen-consuming devices. The present invention provides consumers with a broader choice of catalysts, which, in some cases, catalyze the hydrogen gas evolution reaction at a rate exceeding that of catalysts identified in the prior art.